MitoQ is a mitochondrial-targeted coenzyme Q antioxidant analog that dose-dependently restored cardiac function and reduced infarct size in isolated perfused rat hearts subjected to ischemia reperfusion (I/R). Moreover, mitoQ also dose-dependently attenuated PMA stimulated PMN superoxide (SO) release at the same concentration (10uM) as the cardioprotective dose. NADPH oxidase is the principle source of PMN SO release. We speculate that mitoQ may exert antioxidant effects independent of the mitochondria. Therefore, we hypothesized that inhibition of mitoQ on PMN-SO release will be similar as other coenzyme Q analogs: coenzyme Q1 and decylubiquinone without affecting cell viability. SO release was measured spectrophotometrically from isolated rat PMNs measured by the reduction of ferricytochrome c and were stimulated with 100nM PMA. The absorbance was measured at 550 nm up to 360sec. Positive control samples were given SO dismutase (SOD; 10ug/ml) which inhibited PMA induced SO release by >90%. MitoQ significantly inhibited SO release by 56 + 3% (10uM, n=10 , P